Hot Water

If you place an egg in boiling water then it will cook within minutes – the same egg will still cook at 70°C or at 50°C but it will take longer. You yourself would cook if you spent long enough at these temperatures and so would any animal or plant known.

This makes it more astonishing that some bacteria can live comfortably under these temperatures. It is worth remembering that this is some bacteria only – most will die under high temperatures as readily as animals or plants.

The bacteria that live under high temperatures are thermophiles (Latin for heat lovers) and they live only in water – they are not to be found in arid deserts. The ideal homes for these bacteria are in superheated water – this can be found in two places.

Hot springs such as those in many of Americas national forests, harbour a plentiful supply of bacteria living comfortably at temperatures over 80°C while hydrothermal vents deep under the ocean can reach temperatures of up to 300°C as the boiling point of water is increased due to the vast pressure – it is doubtful to say the least that bacteria can survive up to this amazing temperature but they are certainly found in the cooler waters (up to 120°C) surrounding such vents and these areas are rich in other life forms such as tubeworms which are provided with food by the bacteria.

So why can they do it and we can’t?

The problems of living at such high temperatures are enormous – there is almost no oxygen in the water at such temperatures (but that’s OK, many bacteria do not need oxygen), and proteins and DNA break down rapidly while the delicate internal membrane (made of fatty acids – see below) can actually melt resulting in leakage out of the internal components.

The thermophiles have some neat tricks to combat the last three points.

To keep their proteins from degrading:

·        They replace their proteins much faster than we do

·        Their proteins are optimised to work at higher temperatures – of course, this means that they work more poorly, if at all, at lower temperatures.

To keep their DNA from degrading

·        It is thought that they use special proteins to hold the DNA together – this has not been proven.

To prevent their membrane from melting

·        They use different types of fats, more resistant to heat

Why did we not evolve to deal with these temperatures too?

The answer is a simple but unproven one – the world was once much hotter than it is now and life has evolved for the more prevalent cool conditions. The thermophiles can be thought of as remnants of the most ancient life forms (though they are not exactly the same – they have evolved too).

Importance to us: some of the enzymes from thermophiles are vital to certain areas of science – genetic fingerprinting, for example, would be almost impossible without such enzymes.

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